package stmo.链表;

public class CircleListCheckTest {


    /**
     *  快慢指针判断链表是否有环问题
     */

    public static void main(String[] args) {

        //创建结点
        Node<String> first = new Node<String>("aa",null);
        Node<String> second = new Node<String>("bb",null);
        Node<String> third = new Node<String>("cc",null);
        Node<String> fourth = new Node<String>("dd",null);
        Node<String> fifth = new Node<String>("ee",null);
        Node<String> six = new Node<String>("ff",null);
        Node<String> seven = new Node<String>("gg",null);

        //完成结点之间的指向
        first.next = second;
        second.next = third;
        third.next = fourth;
        fourth.next = fifth;
        fifth.next = six;
        six.next = seven;

        //产生环
        seven.next = third;

        Boolean circle = isCircle(first);
        System.out.println("链表中是否有环："+circle);
    }

    private static Boolean isCircle(Node<String> first) {

        Node fast = first;
        Node slow = fast;

        while (fast != null && fast.next != null) {
            fast = fast.next.next;
            slow = slow.next;
            if (fast == slow) {
                return true;
            }
        }
        return false;
    }


    private static class Node<T> {

        T item;

        Node next;

        public Node(T item, Node next) {

            this.item = item;
            this.next = next;
        }
    }

}
